1. Field of the Invention
The present invention relates to a roller blind structure comprising an elongated preferably tubular member having at the ends thereof axially extending studs which are rotatably and displaceably received in slots provided in two spaced apart brackets provided to be secured to the upper part of a window casing or the like such that said elongated member when rotated in a clockwise direction moves in one direction along said slots but when rotated in an anticlockwise direction moves in the opposite direction along said slots. The elongated member is rotated by means of a cord attached to the hub of a flanged reel secured to one end of said elongated member and a fabric is secured to said elongated member and wound up thereon in a direction opposite to that of said cord such that when fabric is unrolled from the elongated member, the cord is wound upon the reel and vice versa. If the fabric is wound upon the elongated member in such a direction that it is unrolled from said member when the latter is rotated such that it moves towards the window the fabric will seal against said window casing when the fabric goes down.
2. Description of the Prior Art
The U.S. patent application Ser. No. 06/095,039, now U.S. Pat. No. 4,347,885, describes a roller blind structure of the kind referred to and to achieve that the cord will reel and unreel in a proper manner without forming loops and without leaving the reel there is according to said U.S. patent application provided a sleeve having an axially extending slot and said sleeve is mounted over said reel to be displaced therewith but without being rotated therewith. To this end such a sleeve has an axially projecting portion to engage a surface of said bracket to allow said sleeve to be displaced but not rotated and thus said sleeve has to have a precise orientation when mounted over the reel. It has proven that this is no problem when the roller blind is first installed as the installation is carried out with the aid of a written instruction. When--however--the elongated member with the fabric screen has been taken down for instance for cleaning the screen or changing the cord, the installation instruction in most instances is not available and as a consequence thereof the sleeve is often improperly mounted and as a result thereof the blind will not function and may also be damaged. It has also been found that the sleeve can be stuck in one position especially when the cord is rapidly operated and also in this case the proper function of the blind is in danger. The sleeve must be made with a certain clearance in all directions to be able to move properly but it cannot be avoided that the sleeve offers such a resistance that the force which has to be applied to the cord for winding up the screen will reach an unacceptable level.